Drop on demand ink jet technology is widely used in the printing industry. Printers using drop on demand ink jet technology may use a plurality (i.e., an array) of electrostatic actuators, piezoelectric actuators, or thermal actuators to eject ink from a plurality of nozzles in an aperture plate (nozzle plate). Even though they are more expensive to manufacture than thermal ink jets, piezoelectric ink jets are generally favored, for example because they can use a wider variety of inks.
Piezoelectric ink jet print heads include an array of actuators (i.e., piezoelectric elements or transducers). One process to form the array includes detachably bonding a blanket or bulk piezoelectric layer including a lead zirconate titanate composition to a transfer carrier with an adhesive, and dicing the blanket piezoelectric layer to form a plurality of individual piezoelectric elements. A plurality of dicing saw passes can be used to remove all the piezoelectric material between adjacent piezoelectric elements to provide the correct spacing between each piezoelectric element.
Piezoelectric ink jet print heads can typically further include a flexible diaphragm to which the array of piezoelectric elements is bonded, for example with an epoxy adhesive. The diaphragm may be a metal layer that functions as a lower electrode that is common to a plurality of actuators, or a non-metal layer coated with a metal layer that provides an individual, electrically conductive lower electrode for each actuator. When a voltage is applied across one of the actuators, the actuator bends or deflects, causing the diaphragm to flex which expels a quantity of ink from a chamber through a nozzle. The flexing further draws ink into the chamber from a main ink reservoir through an opening to replace the expelled ink.
The bulk piezoelectric composition can have a thickness from about 2 mils to 4 mils (50 micrometers, μm, to 100 μm), and a stainless steel diaphragm having a thickness that is from about 20 μm to 50 μm thick. The bulk piezoelectric layer can be diced into square or parallelogram shapes to conform to square or parallelogram body chambers. During printing, ink is ejected from the body chambers through the nozzles in the aperture plate.
Increasing the printing resolution of an ink jet printer employing piezoelectric ink jet technology is a goal of design engineers. One way to increase the jet density is to increase the density of the actuators. In one implementation, a thin film actuator array may be bonded to relatively long and narrow body chambers to insure robustness of the diaphragm and to control vibrational modes of the diaphragm.
Forming relatively small, thin actuators and subsequently attaching them to a diaphragm becomes more difficult with decreasing actuator sizes and thicknesses. While microelectronic fabrication of printhead structures would provide precise control of resulting structures, such methods are volume sensitive and capital intensive which may preclude their use for low volume or custom products.
Current thin film piezoelectric systems utilize a much thinner diaphragm, on the order of 1 to 3 μm. Because of this it is desirable to have a relatively long, thin body chamber to insure robustness of the diaphragm and to control the vibrational modes of the diaphragm. Further, current thin film printhead fabrication processes generally use silicon wafers or quartz/glass panels in a microelectronic fabrication process to achieve the process control required for such films. Microelectronic processing can be volume sensitive and capital intensive. This can preclude its use for low volume or custom products.
A method for precise formation of thin film actuators and an associated printhead structure is desirable.
There is also a need to fabricate high quality BNKT-BMT thick films in the range of 5-50 μm which will cover the important commercial technological gap between the thin films and the bulk ceramics. Conventional tape casting and screen printing techniques have been widely used for preparing piezoelectric thick films, which generally require high temperature annealing or sintering process above 1000° C. Unfortunately, such an extremely high temperature is unacceptable for the membrane metal substrate due to a severe chemical reaction and oxidation of the substrate materials. Therefore, extensive efforts have previously focused on reducing sintering temperature of the thick films using sintering aids in the slurry or the paste.
However, sintering aids have induced the formation of a second non-piezoelectric phase in the final sintered films, which can lead to a substantial damaging effect on the electrical and physical properties of the films and usually need to process under reducing conditions to match the temperature limits of the substrates.
To solve these drawbacks, provided herein is a simple process for high quality BNKT-BMT thick films using a chemical solution modified hybrid deposition technique, that is, the use of multiple infiltration process using the same composition BNKT-BMT solution without any additional sintering aids. As further discussed in the detailed description below, with this technique, the annealing temperature of the thick films is lowered to 700° C. with much enhanced piezoelectric performance of the films.